a, Titration histograms of 209Bi-tagged MHC class II antibody with mouse PBMCs and titration curves in B cells and T cells. b–e, Titration histograms at the optimal concentrations. b, 209Bi-tagged p-STAT3 antibody of 1,000 ng/mL with CD33+CD14+ monocytes in human PBMCs with stimulation of 100 ng/mL IL-10 as positive control and without stimulation as negative control. c, 209Bi-tagged p-histone H3 antibody of 2,000 ng/mL with mesodermal progenitors derived from human embryonic stem cells on day 6 of differentiation as positive control and cardiomyocytes derived from human embryonic stem cells as negative control. d, 209Bi-tagged IFN-γ antibody of 1,000 ng/mL with natural killer cells with stimulation of 50 ng/mL IL-12 and IL-18 as positive control and without stimulation as negative control. e, 209Bi-tagged anti-PE antibody of 1,000 ng/mL with PE-conjugated CD3-antibody-stained T cells and B cells in human PBMCs as positive and negative controls, respectively. cps, counts per second.